Laser interferometry is currently widely used for fine measurements of a few hundredths of a light wavelength resolution in the manufacture or processing of high precision surfaces or tools, such as mirrors and lenses and the like, integrated circuit wafers, such as memory chips, and similar devices. In the manufacture of wafers and the like, for example, it is desired to proceed in the processing along parallel lines of a few sub-microns width, and it is important to know the position at all times and to ensure that the processing is taking place exactly along these lines within a few percent. Today, the tracking of position in such scanning processes as in the manufacture of wafers and the like, is effected through laser interferometry. Laser interferometers, however, are designed for one-axis measurement and require very expensive and stable laser sources, and optics. In order to get down to the order of nanometer resolution, this has to be divided into several hundred units. This subjects the system to inaccuracies since the wavelength of the laser may vary as a result of temperature variations, airflow condition changes, and so forth. Often, moreover, it is required that such high precision measurements be done in a vacuum which is expensive and cumbersome.
Other applications where very good precision is required are, for example, in the manufacture of master disks for CD-disk reproduction and the like. In the diamond machining and finishing of satellite telescopes and the like, similar orders of precision are required as well.
Particularly since the advent of scanning tunneling microscopes, described for example by G. Binnig and H. Rohrer in Helev. Phys. Acta, 55, 726 (1982), and atomic force type microscopes, as in U.S. Pat. No. 4,724,318, the imaging of atomic surfaces and the like has become readily feasible, opening the door to nanometer position resolution.
In publications by Higuchi and others, such as in "Crystalline Lattice for Metrology and Positioning Control", Proceedings IEEE Micro Electro Mecahnical Systems, page 239-244, such equipment has therefore been used with an atomic surface disposed on a moving table, wherein the tunneling microscope sensor counts the number of atoms on the passing surface in the X and/or Y direction to come to different predetermined positions or locations on the surface. To effect position locking for each new position attained, the table is rotated, always being in sinusoidal vibration.
This operation, however, does not give real-time continual sensor position location measurements over the surface; and it is to the provision of such continual locations measurement that the invention is directed, and at resolutions of the order of 0.01 nanometers and below--namely one tenth to one hundredth of the resolution of laser interferometric position measurements. The invention, furthermore, unlike Higuchi, et al, obviates the table vibration position locking and provides for position locations by sensor oscillation about a reference point. The advantages over laser interferometry, in addition to the greatly improved resolution, reside also in the obviating of the need for an optical system, its complexity and its errors due to temperature variations and the like.